In conventional buildings, many window glasses almost use a single plate glass. The heat efficiency of this construction is very bad. Since a plate glass easily allows heat transfer, a place in the sun in a room becomes hot; in contrast, an inner place of the room is left cold. If there is a non-uniformity of the temperature in a room, effectiveness of heating and cooling equipment also becomes bad, energy efficiency as well is poor. This means that heat is not used effectively for maintaining an appropriate room temperature.
As described in Patent Literature 1, an invention of an interior glass skin structure for a double glass skin has also been disclosed. This invented structure is, by forming a double skin structure by placing an inner glass (interior glass) on the room side of a plate glass (exterior glass), capable of reducing the thermal load on the window surface caused by insolation or the like during cooling, and enhancing the heating efficiency by heat recovery of the air warmed by insolation or the like during heating. In particular, the use of warm air in winter season is an energy saving method that can be workable through the passage of intake of the air from a room, heat exchange in the intermediate cavity, and then exhaust into the room; it is therefore difficult to build this configuration easily in the conventional method.
Upon making a window glass the double skin structure, first, it is necessary that cleaning of the glass and the maintenance of blinds in the intermediate cavity can be implemented without providing a maintenance deck. Note however that this need has been fulfilled by the invention described in Patent Literature 1. Next, it is also necessary that the control of the air in the intermediate cavity provided between the exterior glass and the interior glass should be easy and reliable to endure a long-term practical use with little maintenance.
To control the air at the intermediate cavity, the intake-exhaust ports are provided at the top and bottom on the exterior glass side, and the ports are opened or closed manually or automatically to allow intake or exhaust of the outside air. In the case of a curtain wall of aluminum (detachable wall), there is a system in which an outside air introduction mechanism is incorporated between horizontal members or between vertical members. In this system however, prediction of the effect is difficult because the system is a natural ventilation system, of which intake-exhaust performance is dependent on the variation of the wind direction or the wind speed.
The interior glass side that does not contact with the outside air directly should have at least earthquake-resistant performance. However, the performance of wind pressure resistance should be considered, because the intermediate cavity takes in the outside air. The performance of wind pressure resistance of the interior glass is determined by the wind speed according to the area of the intake-exhaust port on the exterior glass side under the condition of the port being open; it is necessary to assume a several-fold value of the determined value from the point of view of safety. In addition, the wind speed tolerable in use, though dependent on the area of the intake-exhaust ports, is about 10 meters per second; in particular, when a blind is installed in the intermediate cavity, the intake-exhaust becomes difficult when the wind speed exceeds 10 meters per second. Further, it is also difficult to install a filter at the intake-exhaust port when the ports take in the outside air is considered; and the number of the maintenance operations for the inside will increase.
In the case of natural intake-exhaust, a long-time-assured performance is also required with respect to a reliable operation of complete sealing and opening under the designed wind pressure. If not used for a long time, the sealing material may stick or the operating mechanism may have a trouble; a maintenance plan assuming it is also necessary. In addition, if the intake-exhaust ports are left open at the time of a strong winds or rain particularly a storm, the internal pressure of the intermediate cavity increases, affecting the blind and the interior glass developing into a big problem. An attempt to overcome the problem described above cannot escape from a high expenditure in the present circumstances.